In the 1880s, an Academy Standard film format was created for 35 mm film, wherein the film stock had two rows of perforations, each film frame had an aspect ratio (width divided by height) of 1.33 to 1, and the film frames were spaced apart by 4 perf. spacings (0.750 inch). This format was widely adopted in the 1890s. When soundtracks were added, the frame width and height were reduced, and an aspect ratio of 1.37 to 1 was adopted. In the 1950s, a new projection aspect ratio called Wide Screen Academy Format was adopted, wherein the same film was used, but the projector film gate mask was changed to have a smaller height than previously for an aspect ratio of 1.85:1. The film frames recorded by a camera and projected by the projector, were still of the same size and still spaced apart by 4 perf. spacings, but about 40% of the length of the film was not projected and therefore was wasted. It has been recognized that about 25% of the film used in the current 4 perforation format could be saved by spacing the frames by 3 perforations along the length of the film. Applicant has recognized that 37.5% of the film could be saved by spacing the film frames by 2.5 perforations. However, spacing of the film frames by a non-integer number of perforations, such as 2.5 perforations, can give rise to problems during film processing.
During projection onto theater screens, the film frames are advanced through the projection film gate by an intermittent sprocket wheel that is rotated in 90.degree. steps by a Geneva mechanism. Geneva mechanisms wear, which results in turning the intermittent sprocket wheel by slightly more or less than 90.degree. in each step, which results in significant film registration error. The precision of registration required during film processing, when an internegative is made that may produce thousands of release prints, is greater than that which is acceptable during projection. As a result, in film processing, registration pins are used to precisely position or register the film at the film gate.
When the film briefly comes to rest at the film gate, a pair of registration pins is projected through the film perforations. The registrations pins slightly shift the film position to precisely register the film frame. Where the film is advanced by an integer number of perforation spacings (such as 4) in each step, a perforation will be aligned with the registration pin at each film frame. However, where the film is advanced by a noninteger number of perforation spacings (e.g. 2.5), then a registration pin would punch a hole in the film at every other film frame (this is unacceptable). It would be desirable if the well accepted technique of pin registration could be used even for a system that advanced the film in steps of a noninteger number of perforation spacings such as 2.5.